Detectors to enable calibration of radiation producing equipment are well known in the art. Typical detectors are manufactured by th Victoreen Instrument Division of V & L, Cleveland, Ohio. However, no detectors in the prior art are true human tissue equivalents. When it is desired to calibrate high energy electron and/or photon beams such as those used in the treatment of cancer, the standard method is to use an air ionization chamber in a water phantom. The beam intensity is then calculated by the use of theoretical relationships using theoretically calculated electron stopping power ratios.
The air in an air chamber is about 1000 times less dense than actual tissue so that the volume of the detector or probe needs to be about 1000 times larger than the volume of tissue that acquires the same energy deposition by ionization. Such a large probe disrupts the radiation field fluence, and the secondary electron flux and introduces error into the measurement system.
In other applications it is also desirable that the radiation measuring probe or detector be equivalent to the structure to be subjected to radiation so that theoretical correction factors and other inaccuracies do not have to be employed.